Two threshold uplink rate control to enable uplink scheduling

ABSTRACT

A wireless communications network has a plurality of terminals and at least one base station which transmits data to each one of said plurality of terminals on a wireless downlink and receives data from each one of said plurality of terminals on a wireless uplink. One of the terminals sends a rate request to the base station. The rate request requests that the data rate on the wireless uplink for the terminal be changed. In response to the rate request, the base station sends a rate grant to the terminal. The rate grant indicates whether or not the terminal may change the data rate on the wireless uplink.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of wirelesscommunications. More particularly, the present invention relates touplink enhancements in the air interface between a terminal and a basestation in a wireless communications network.

2. Description of the Related Art

The air interface between a terminal and a base station in a wirelesscommunications network relates directly to the achievable level ofperformance of the network. It is essential to have a lowsignal-to-interference ratio (SIR) requirement for sufficient linkperformance with various coding and diversity solutions in the physicallayer, since the physical layer defines the fundamental capacity limitsof the air interface.

In 3^(rd) generation wireless communications systems, such as thatspecified by Release '99 or subsequent releases of the 3rd GenerationPartnership Project joint standardization project (www.3gpp.org), thephysical layer is not designed around a single service, such as voice;more flexibility is necessary to enable dynamic scheduling of multimediaservices. In Release '99, 3GPP TS 25.211-25.215 describes the physicallayer, 3GPP TS 25.331 describes the radio resource control protocol, and3GPP TS 25.133 describes requirements for radio resource management,which are incorporated herein by reference in their entirety.

FIG. 1 illustrates the architecture of the radio access network thathandles all radio-related functionality in Release '99. User Equipment(UE) 11 is connected via the radio interface to a respective first NodeB 21-1. First Node B 21-1 converts the data flow between the lub andradio interface and also participates to a limited extent in radioresource management. First Node B 21-1 and second Node B 21-2 are bothconnected to the same Radio Network Controller (RNC) 31-1 via the lubinterface and share the same radio resource management. RNC 31-1 isresponsible for the control of the radio resources in its domain, i.e.first node B 21-1 and second node B 21-2. Although only two are shown inFIG. 1, there will normally be more than two Node B's connected to asingle RNC. Each group of Node B's and single RNC constitute a radionetwork subsystem (RNS) and although only two are shown in FIG. 1, therewill normally be a large number of RNS's in a radio access network.Collectively, the RNCs are the service access points for all services(including, for example, management of connections to UE 11) that theradio access network provides to a core network (not shown) via the luinterface. The elements shown in FIG. 1 are defined at the logicallevel, but may have a similar physical implementation as well.

In Release '99, there is little flexibility in scheduling thetransmissions on the uplink from UE 11 to Node B 21. The physical layerrate signaling terminates at Node B 21. The RRC limits the TFCS usingvarious signaling formats and UE 11 can only use the allowed TFCS. Thishas the disadvantage that various measurements and UE RRC reports takento SRNC, processed and sent to UE 11, all over a frame structuremeasured in milliseconds.

In Release '99, scheduling changes can be made in the uplink using theunacknowledged signaling mode in Radio Resource Control (RRC) with aspecified activation time. Alternatively, the RRC includes the abilityto control and limit the Transport Format Combination Control usingvarious signaling formats. The transport format combination control canbe sent in transparent mode on its own transport channel in every TTI.Transport format combinations can be indexed, with a list ofallowed/non-allowed combinations or an full open set of combinations.For an example of the specifications, including the maximum of time thatshould pass after a signaling message is received due to processing inthe UE before the new combination is assumed, see 3GPP TS 25.331 v3.8.0, Section 13.5.

This method of using the RRC ability to limit the TFCS can be slow toadapt to changes in the network, such as in the amount of data to betransmitted between network elements. Also, since the method isdependent on RRC controlled by the RNC, it susceptible to processingbottlenecks and other factors affecting the performance of the RNC.

BRIEF SUMMARY

In a first aspect of the preferred embodiment of the invention, awireless communications network comprises a plurality of terminals andat least one base station which transmits data to each one of saidplurality of terminals on a wireless downlink and receives data fromeach one of said plurality of terminals on a wireless uplink. At leastone of said plurality of terminals sends a rate request to said basestation, said rate request requesting that the data rate on the wirelessuplink be changed. Said base station, in response to said rate requestfrom said at least one of said plurality of terminals, sends a rategrant to said at least one of said plurality of terminals, said rategrant indicating whether or not said at least one of said plurality ofterminals may change the data rate on the wireless uplink.

In a second aspect of the preferred embodiments, the present inventionprovides a reliable data rate control method and wireless communicationsnetwork including a radio access network which transmits data from abase station to a terminal in a wireless downlink and receives data fromthe terminal to the base station in a wireless uplink. In this aspect ofthe preferred embodiments of the invention, the terminal is adapted toreceive two thresholds specifying the limits on the data rate on saidwireless uplink, a first one of said two thresholds specifying a limitfor said data rate that may be requested by said terminal and a secondone of said two thresholds specifying a limit for said data rate thatmay be requested by said base station. The terminal sends a rate requeston the wireless uplink from the terminal to the base station, said raterequest requesting that the data rate on said wireless uplink beincreased or decreased within the limits of said first one of said twothresholds. The terminal increases or decreases the data rate on saidwireless uplink in accordance with said rate grant in response to a rategrant received from said base station, said rate grant indicatingwhether or not said data rate on said wireless uplink may be increasedor decreased as requested in said rate request.

In another aspect of the preferred embodiments of the invention, thewireless communications network including a base station which transmitsdata to a terminal on a wireless downlink and receives data from aterminal on a wireless uplink carries out a method. The method comprisessending a rate request from said terminal to said base station, saidrate request requesting that the data rate on the wireless uplink beincreased or decreased; and in response to said rate request from saidterminal, sending a rate grant to said terminal, said rate grantindicating whether or not said terminal may increase or decrease thedata rate on the wireless uplink.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments are described below with reference to theaccompanying drawings, in which:

FIG. 1 is a block diagram illustrating the uplink connection of userequipment in a radio access network according to 3GPP Release '99.

FIG. 2 graphically illustrates an example of the two RRC controlledthresholds applied to the transport format combination set according tothe preferred embodiments of the invention.

FIG. 3 graphically illustrates a data rate control concept utilized inthe preferred embodiments of the invention.

FIG. 4 graphically illustrates an example of multiple user equipmentrate control according to a preferred embodiment of the presentinvention.

Like reference numerals identify like parts throughout the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The particulars shown herein are by way of example and for purposes ofillustrative discussion of the preferred embodiments of the presentinvention. The description taken with the drawings make it apparent tothose skilled in the art how other various embodiments of the presentinvention may be implemented in practice.

Further, elements are shown in block diagram form in order to avoidobscuring the invention, and also in view of the fact that specificswith respect to implementation of such block diagram arrangements ishighly dependent upon the network environment within which an embodimentof the present invention is to be implemented, i.e., specifics should bewell within the purview of one skilled in the art. Although thepreferred embodiments of the invention are described with reference tothe example system block diagram of 3GPP Release '99 in FIG. 1,embodiments of the invention may be practiced in other wirelesscommunication networks, including but not limited to, subsequent 3GPPspecification releases.

Where specific details (e.g., interfaces) are set forth in order todescribe embodiments of the invention, it should be apparent to oneskilled in the art that the invention can be practiced without thesespecific details. Finally, it should be apparent that any combination ofhardware and software programming can be used to implement embodimentsof the invention and that the embodiments are not limited to anyspecific combination of hardware and software programming.

As known to one skilled in the art, data is conventionally transmittedover the air interface in accordance with radio resource controlsignaling sent by a RNC over lub interface, which signaling includesconfiguration and reservation of radio resources. The Node B 21 performsL1 air interface processing such as channel coding and interleaving,rate adaptation, spreading, etc. The term “rate adaptation” refers torate matching in which the number of data bits to be transmitted isadapted to the number of bits available on a frame and does not refer tothe present invention. See, for example, Section 6.4.2 of the book“WCDMA for UMTS (revised edition)” by Harri Holma and Antti Toskala,published by John Wiley & Sons, 2001 for further discussion of ratematching. It also performs some basic radio resource managementfunctions such as inner loop power control. The RNC 31 terminates theRRC signaling protocol with UE 11. It performs L2 air interfaceprocessing of the data to/from the radio interface. Radio ResourceManagement functions, such as mapping of Radio Access Bearer (RAB)parameters into air interface transport channel parameters, handovers,and outer loop power control are executed in RNC 31.

As described in further detail hereafter, the preferred embodiments ofthe invention have a two threshold rate control by which Node B 21,being closer to the air interface than SRNC 31, can perform limited butfast uplink scheduling operations. The two thresholds for two respectivenetwork elements allow fast and distributed scheduling of data on theuplink. The preferred embodiments of the invention are not limited toany particular signaling method for performing the scheduling over theair interface. An example of the uplink signaling method is provided inU.S. patent application Ser. No. 10/156,751, filed on May 24, 2002,entitled “Method and Apparatus for Distributed Signaling for Uplink RateControl” and commonly assigned to Nokia Corporation, the assignee ofthis application, the contents of such application are herebyincorporated by reference in their entirety.

As a preferred embodiment of this invention, the two thresholds are setwith reference to the combination sets utilized in the Transport FormatCombination Control (TFCC). In 3GPP Release '99, transport formatcombination control is specified in 3GPP TS 25.331 v3.8.0 (2001-09),Section 8.2.5 and data rates correspond to various transport formatcombination sets. Specifically, in the preferred embodiments, RNC 31specifies two transport format combination set (TFCS) thresholds. Inaddition to UE threshold 100, a Node B threshold 200 is also specified.Both Node B 21 and UE 11 are informed of these thresholds. UE 11 isnormally limited to UE threshold 100, but may use the Node B threshold200 as instructed by Node B 21. There is no per se limitation on thevalue of UE threshold 100 and Node B threshold 200. Indeed, either NodeB threshold 200 or both thresholds may include the entire TFCS range.

FIG. 2 graphically depicts the TFCS thresholds. Separate RRC signalingbetween Node B 21 and UE 11 controls TFCS selection and utilization ofthe space above UE threshold 100 and below Node B threshold 200. UE 11can freely select its Transport Format Combination (TFC) from any ofthose in the set below the UE threshold 100. Between the UE threshold100 and Node B threshold 200, Node B 21 can control the limitationsgiven to UE 11. Hence, Node B 21 can selectively schedule the uplinkdata rates of UE 11.

UE 11 is aware of the entire range of possible data rates (TFCS) for thewireless uplink, such as, for example, from 16 kbps to 2 Mbps. The UEthreshold 100 specifies the highest data rate that it can use (withappropriate signaling from RNC), such as, for example, 384 kbps. TheNode B threshold 200 can be set at, for example, 2 MBps, and UE 11 canbe required to send a rate request to Node B 21 for changes in the datarate above 384 kbps. This requirement may be made for all such changes(increase or decrease) or only for increases in the data rate. Node B 21and UE 11 may receive only UE threshold 100 or both UE threshold 100 andNode B threshold 200. In particular, Node B 21 may receive boththresholds, but UE 11 receives only UE threshold 100.

FIG. 3 depicts the data rate control concept utilized in the preferredembodiments of the invention. The bottom portion of FIG. 3 indicates thevalue of rate requests sent by UE 11, the value of the transport formatcombination as indicated by the TFCI value, and the data on the wirelessuplink. The upper portion of FIG. 3 indicates the value of the rategrant signal sent by Node B in response to the rate request.

The sequence of events in the preferred method is as follows. First, UE11 transmits its data along with a rate request (up or down). Node B 21receives the data and the rate request (RR) from UE 11. Then, Node B 21sends a rate grant to UE 11 containing an indication of whether the UE11 may increase, decrease or remain at the current data rate dependingon the received interference conditions or other appropriate trafficmetrics either derived/measured at Node B 21 and/or sent to Node B 21from RRC. In one embodiment, UE 11 may be considered to have returned tothe range of allowed data rates if it is using data rates below thatspecifed by UE threshold 100 (384 kbps in the above example). In such acase, a rate request to decrease the data rate on the wireless uplinkwould not ever be necessary.

Preferably, but not necessarily, the up/down rate request is included atevery TTI period. Preferably, but not necessarily, the up/down/keep rategrant is provided at every TTI period. Alternatively, the rate requestmay be sent when a certain event occurs in UE 11, such as, for example,when the transmit buffer of UE 11 exceeds a certain limit.

FIG. 4 demonstrates a scenario whereby multiple UEs using the twothreshold concept are controlled by Node B 21. In this example, Node B21 controls the first UE's data rate (increasing) and the second UE'sdata rate (decreasing) at regular intervals. In particular, it slowlyredistributes resources between each UE primarily connected to it undercontrol of RNC 31. The changes are gradual as allowed by RRM. A primaryconnection is established so that only one Node B in a network cancontrol one UE.

These preferred embodiments of the invention provide termination closerto air interface than in conventional radio access networkarchitectures. They also provide the advantage of faster processing onL1/L2 between Node B 21 and UE 11. This is because even though the timeintervals are subject on any particular network implementation, the timeintervals of communication frames between UE 11 and Node B 21 aretypically measured in the tens of milliseconds. Thus the speed withwhich the data scheduling on the uplink can be adjusted in the spacebetween UE threshold 100 and Node B threshold 200 is several orders ofmagnitude grater than that which can be achieved when the adjustmentsare dependent on the signaling from RNC 31.

Signaling of the two thresholds to UE 11 is a trivial addition to theRRC protocol and the details thereof are not essential to the invention.One embodiment would be to add the Node B threshold 200 as an optionalextra parameter or information element to the Transport FormatCombination Control (TFCC) message in RRC signaling.

Likewise, signaling of the UE threshold 100 and Node B threshold 200 toto Node B 21 would be an extension of the Node B Application Protocol(NBAP) where the details are not essential. Of course, the notificationof the two threshold to Node B 21 can be carried out in any number ofdifferent ways.

While the invention has been described in terms of its preferredembodiments, it should be understood that numerous modifications may bemade thereto. It is intended that all such modifications fall within thescope of the appended claims.

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 12. A wireless communications networkcomprising: a plurality of terminals; and at least one base stationwhich transmits data to each one of said plurality of terminals on awireless downlink and receives data from each one of said plurality ofterminals on a wireless uplink; wherein at least one of said pluralityof terminals sends a rate request to said base station, said raterequest requesting that the data rate on the wireless uplink be changed;and said base station, in response to said rate request from said atleast one of said plurality of terminals, sends a rate grant to said atleast one of said plurality of terminals, said rate grant indicatingwhether or not said at least one of said plurality of terminals maychange the data rate on the wireless uplink.
 13. A wirelesscommunications network in accordance with claim 12, wherein said atleast one of said plurality of terminals send the rate request alongwith data in the wireless uplink.
 14. A wireless communications networkin accordance with claim 12, wherein said base station sends said rategrant in said wireless downlink.
 15. A wireless communications networkin accordance with claim 12, wherein said rate grant sent by said basestation depends on interference conditions received at the base station.16. A wireless communications network in accordance with claim 12,wherein said rate grant sent by said base station depends on trafficmetrics derived and/or measured at the base station.
 17. A wirelesscommunications network in accordance with claim 12, wherein said networkfurther comprises a base station controller and said rate grant sent bysaid base station depends on traffic metrics sent to said base stationfrom said base station controller.
 18. A wireless communications networkin accordance with claim 12, wherein said rate request requests that thedata rate on said wireless uplink be increased and, in response to arate grant received from said base station, said rate grant indicatingthat said data rate on said wireless uplink may be increased asrequested in said rate request, increases said data rate on saidwireless uplink in accordance with said rate grant.
 19. A wirelesscommunication network in accordance with claim 18, wherein said terminalmay decrease the data rate on said wireless uplink without a separaterate grant from said base station.
 20. A wireless communications networkin accordance with claim 12, wherein the air interface between theterminal and the base station is wide band code division multiple access(WCDMA).
 21. A wireless communication network in accordance with claim12, wherein said at least one of the plurality of terminals is providedwith two thresholds limiting the data rate on the uplink and the raterequests sent by said terminal are limited to one of the two thresholds.22. A wireless communication network in accordance with claim 21,wherein each one of said plurality of terminals is provided with saidtwo thresholds limiting the data rate on the uplink and said basestation controls the data rate on the uplink from each one of saidplurality of terminals in response to a rate request from any one ofsaid plurality of terminals.
 23. In a wireless communications networkincluding a base station which transmits data to a terminal on awireless downlink and receives data from a terminal on a wirelessuplink, a method comprising: sending a rate request from said terminalto said base station, said rate request requesting that the data rate onthe wireless uplink be changed; and in response to said rate requestfrom said terminal, sending a rate grant to said terminal, said rategrant indicating whether or not said terminal may change the data rateon the wireless uplink.
 24. A method in accordance with claim 23,wherein said terminal sends the rate request along with data in thewireless uplink.
 25. A method in accordance with claim 23, wherein saidbase station sends said rate grant in said wireless downlink.
 26. Amethod in accordance with claim 23, wherein said rate grant sent by saidbase station depends on interference conditions received at the basestation.
 27. A method in accordance with claim 23, wherein said rategrant sent by said base station depends on traffic metrics derivedand/or measured at the base station.
 28. A method in accordance withclaim 23, wherein said rate grant sent by said base station depends ontraffic metrics sent to said base station from said base stationcontroller.
 29. A method in accordance with claim 23, wherein the airinterface between the terminal and the base station is wide band codedivision multiple access (WCDMA).
 30. A method in accordance with claim23, wherein said terminal is provided with two thresholds limiting thedata rate on the wireless uplink and the rate requests sent by saidterminal are limited to one of the two thresholds.
 31. A method inaccordance with claim 23, wherein said rate request requests that thedata rate on said wireless uplink be increased and, in response to arate grant received from said base station, said rate grant indicatingthat said data rate on said wireless uplink may be increased asrequested in said rate request, increases said data rate on saidwireless uplink in accordance with said rate grant.
 32. A method inaccordance with claim 31, wherein said terminal may decrease the datarate on said wireless uplink without a separate rate grant from saidbase station.